Metal cleaning



" Nov. 23, 1943.

M. c. PECSOK 2,335,196

METAL CLEANING Filed Sept. 9, 1940 INVENTOR.

1 MICHAELCPECSOK M, {QM vQw/ ATTORNEYS Patented Nov. 23, 1943 METAL CLEANING Michael C. Pecsok, Peninsula, Ohio, assignor to The Osborn Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application September 9, 1940, Serial No. 355,969 4 Claims. (Cl. 29-81) This invention relates, as indicated, to metal cleaning, and more particularly to a. method 01' removing scale from metal sheets.

A great variety of methods for cleaning metal sheets, and particularly sheet or strip steel. has been proposed and employed in the past. However, that which has become generally accepted and is now almost universally employed involves the passage of the sheets through pickling tanks containing acid for the purpose of removing the scale. The use of pickling tanks has many disadvantages and such tanks would not now be still employed if any practical alternative had previously been available.- In general practice the sheets as they come from the mill are subjected to a water spray, stitched" together and run as a continuous strip through breaker rolls for the purpose of breaking the scale into particles, and then passed through the pickling tanks. Since it is not. possible to pass the strip through the tanks at the same speed with which the same passes through the breaker rolls, a bottle-neck results. Fumes from the tanks are injurious to the operators and seriously afiect adjacent machinery and the building in which they are installed, by the promotion of rusting.

The quality of the sheets "is also lowered due to hydrogen embrittlement. Cost of treatment often average about 35 per ton of sheet. and

maintenance charges are also high. To an increasing degree, legislation restricting the dumping of spent pickling acid causes further difficulty and expense.

It is, therefore, a primary object of this invention to provide a method. of cleaning metal surfaces, and particularly steel sheets, which will obviate the necessity for any pickling operation whatsoever.

Another object of this invention is to provide a method of removing scale which will be quick and inexpensive in operation and require the use of a relatively small amount of floor space.

A further object is to provide a method of cleaning metal surfaces which will not be injurious to the quality of such metal surfaces, but on scription set forth in detail one approved method of carrying out the invention, such disclosed method, however, constituting but one of various ways in which the principle of the invention may be used,

In said annexed drawing:

Fig. 1 illustrates in diagrammatic fashion the passage of a metal sheet through brushing mechanism in accordance with this invention; and

. Fig. 2 shows, also diagrammatically, the water spray and breaker rolls through which the metal sheet will desirably pass prior to passing through the brushing mechanism.

Such mechanism may comprise pairs of rolls I, 2 and 3 between which sheet I is caused to pass. A second sheet 4 is shown stitched to sheet 4. Between rolls I and 2 is roll 5 adapted to engage the lower surface of the sheet while a similarroll 6 between rolls 2 and 3 is adapted to engage the uppersurface of such sheet. Rotatably'mounted with their axes parallel to the axes of rolls 5 and 6 are rotary brushes 1 and'8, of the pairs 1, 2

whereby their relationship to the upper rolls may be adjusted. Rolls 5 and 6 are carried by yd ll p ers l0 and ii respectively, roll 6 the contrary will leave the same in excellent condition for plating, such as galvanizing or tinning, whether hot plating or electrolytic,

Other objects of this invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends. said invention, then, consists of the steps hereinafter .fully described pointed out in the claims.

The annexed drawing and the following deand particularly I being supported from above. It is also contemplated that alternatively brush 8 be mounted on hydraulic means and roll 6 supported by screw adjusted means, as are the other upper rolls.

The sheet 4 'is firmly gripped between the paired rolls to maintain such sheet under tension and in tight engagement with rolls 5 and 6 over which it is flexed. To this end rolls 2 may be driven at a slightly greater speed than rolls l and rolls 3 at a slightly greater speed than rolls 2, say 1%. However, especially with the thinner gauges of sheet, sufilcient tension may often be obtained with all the rolls revolving at approximately the same speed. ,To pro" vide for the passage of welds or stitches, such as l2, through the rolls where two sheets have been welded or stitched together, thickness detector switches l3 are provided before the rolls opera.-

tive to cause the opening of solenoid controlled 7 and I i may be momentarily retracted to permit the passage of the weld or stitch.

Brushes l and 8 will generally be operated in a clockwise and counterclockwise direction, respectively, as viewed in the drawing, and preferably at fairly high speeds, as in the vicinity of 3000 R. P. M. The brushing elements of these brushing stations, rolls of widths are fed through keep the ends 2 rotary brushes may desirably be formed of densely packed tempered wires protruding radially about one to two inches beyond the end flanges. An 11 inch diameter brush with an 8 inch opening has been found quite suitable.

The water spray l1 and breaker roll assembly comprising a plurality of breaker rolls l8, illustrated in Fig.2, may be of the conventional type well known in the art,the sheet passing therethrough being relatively sharply flexed to aid in breaking up the scale into small particles.

In carrying out my invention the sheets as they come from the mill will preferably first be given a harsh water spray while they are at a relatively high the scale. It has been found desirable to spray the sheets while they are still at a temperature just insufficient to substantially volatilize the water spray, or at a temperature somewhat higher than customary. passed through conventional breaker rolls to further break up the scale into particles. From such rolls, and without slackening ofspeed, the sheet next passes through a brushing station of the type illustrated and described above. No pickling step is necessary. The wire bristles of the rapidly rotating brush engage the convex surface of the flexedsheet and lift or pick, off the particles; of, scale. adhering thereto. Such flexing is necessary to, expose the edges of the particles of scale to permit'their removal since such scale is too hard to be readily cut by the wire bristles. To this end it has been found advisable to flex the sheets fairly sharply at the from about 16 to 22 inch radius being generally suitable although such dimensions will vary considerably depending on the thickness of the sheet. In addition to removing the scale the brush also serves to burnish the surface of the sheet, lessening its susceptibility to rusting and corrosion. This is believed to be due to the tendency of the relatiyely soft ferrite to be,spread.over the grain boundaries in the metal surface, reducing the opportunity for penetration of deleterious elecleaning the upper and lower surfaces of the sheet it is of course obvious that further such stations may be employed if desired, and likewise additional brushing units may cluding fiber or fabric brushes and the like, for the purpose of polishing the sheet andproducing a high finish after the scale has been removed.

In order to provide uniform brushing of the metalsurface it is necessary that the sheet be flexed tightly over the rolls in order to present a level surface crosswise of the sheet to be engaged by the brushing element. Likewise, to give good results, 'a brush may be provided with conditioning means such as a' rectangular or cylindrical stone adapted to be reciprocated relatively thereto to maintain the wire bristles at a uniform length. Clearly when sheets of various the brushing station the brushes would be worn' down in un uneven manner if some such conditioning means were not provided. In additio such conditioning will of the wires substantially squared across to provide a contour best suited to engage and remove the particles of scale.

The flexing of the sheet stretches or tensions the convex surface thereof to a degree that the scale cannot equal so that the coating of scale is broken into particles presenting their exposed temperature to aid iniloosening,

The sheets may next be of rejection of sheets for stampings ents. In addition to the bru'sh'stations shown for v be employed, in-

maintained in the preceding water edges to the action of the brush. The flexing may, in some instances, even be suflicient to cause such edges tobe slightly raised from the metal surface.- In any case, the flexing of such particles puts them under a strain which greatly facilitates their removal by the ends of the wire bristles.

Adsorption of gases, whether hydrogen or oxygen, tends to cause embrittlement of the metal and loss of ductility. This is a serious cause and deep drawings as well as accounting for muchloss as scrap of stampings which have torn. Pickling has'long been known to promote such deleterious action. Since the gases are usually adsorbed and penetrate the metal at the ferrite grain boundaries the brushing action which tends to spread the ferrite so as to seal off the carbide particles also reduces the opportunity for the penetration of such gases.

During electrolytic plating, bubbles of hydrogen tend to form in the interstices between the ferrite grain particles with the resultant appearance of pin-holes in the plate. In hot plating, gas which has been adsorbed is driven out and likewise causes lack of adhesion at such points. By sealing ofi the carbide particles all such dif ference of polarity phenomena may be avoided and a much more satisfactory product obtained. Furthermore, while brushing tends to remove a portion of the carbide'from the metal surface there is no pitting of the surface comparable to that produced by the usual pickling operation.

Even when ideal conditions have not been spray step, it is possible to sufilciently remove the scale to obviate the necessity of a subsequent pickling operation. When, however, the sheets have been handled in the preferred manner above indicated, the scale may be entirely removed and a metallic surface produced which isideal for subsequent plating operations, and the like.

While the foregoing description has been particularly concerned with the treatment of steel sheets, it will be understood that surfaces of other metals, such as copper and aluminum, may likewise be advantageously subjected to the treat- I ment of my invention.

1. Pickling is avoided.

(a) No injurious fumes.

(b) A smooth and unpitted surface pro-,

duced.

(0) Much less floor space required.

((1) Greater speed of operation (may be operated at same speed as breaker rolls).

(8) Saving, in cost of treatment.

(I) Lower maintenance both of equipment and building.

2. In galvanizing, tinning, cadmium plating, and the whether hot or electrolytic, the plate adheres much more uniformly and tenaciously to. a surface prepared in accordance with my invention.

'3. A smooth, non pitted surface is provided which is not so readily injured by rust and corrosion.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein 'disclosed, provided those stated by any of the following claims or sheet which comprises spraying the sheet with water as it comes from the mill, such sheet being at a high temperature just insuflicient to volatilize such water spray, passing such sheet through breaker rolls to break the scale into particles, flexing such sheet over a roll to raise the edges of such particles, and brushing the flexed portion of such sheet with a rotary brush disposed on an axis parallel to such roll to detach such particles. 1

2. The method of removing scale from a. metal sheet which comprises arcuately flexing such sheet over a roll having a radius of from about 16 to about 22 inches, and brushing the convex surface of the arcuately flexed portion of such sheet with a'rotary brush disposed on an axis parallel to such roEl.

v3. The method of removing scale from a metal sheet which comprises arcuately flexing such sheet over a roll having a radius of from about 16 to about 22 inches, and brushing the convex suri'ace of the arcuately flexed portion of such sheet with a cylindrical rotary wire bristle brush disposed on an axis parallel to such roll and retating at a speed on the order of about 3000 R. P. M.

4. The method of removing scale from a metal sheet which comprises flexing such sheet at a substantial angle and brushing the convex sur- 1 face of the flexed portion thereof with a rotary brush disposed on an axis parallel to the line of flexing of such sheet and rotating at a speed on the order of about 3000 R. P. M.

MICHAEL C. PECSOK. 

